Mirror illusion reduces motor cortical inhibition in the ipsilateral primary motor cortex during effortful unilateral wrist flexion with shortening muscle contraction

Zult, T. (Tjerk) (2013) Mirror illusion reduces motor cortical inhibition in the ipsilateral primary motor cortex during effortful unilateral wrist flexion with shortening muscle contraction. thesis, Human Movement Sciences.

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Abstract

Objective: Mirror training to strengthen muscles of the affected limb is a promising therapeutic strategy for patients who suffer from unilateral orthopaedic and neurological conditions, although the neural basis for therapeutic effects is largely unknown. To elucidate the neural mechanisms, the present study investigated mirror-induced corticospinal and cortical responses in the resting left flexor carpi radialis (FCR) during rest and forceful shortening contractions of the right wrist flexors. Methods: Corticospinal excitability and short-interval intracortical inhibition (SICI) of the right primary motor cortex (Ml), and interhemispheric inhibition (IHI) from left to right Ml were measured in young healthy right-handed adults (N = 27) when vision of both forearms was blocked (no-mirror condition) and when the mirror was used to create the illusion of seeing the left hand by actually viewing the mirror image of the right hand (mirror condition). Results: Corticospinal excitability increased during contractions, but there was no mirrorinduced effect. However, the contraction effect disappeared when corticospinal excitability was expressed relative to background electromyogram activity of the left FCR. Viewing the mirror image of the contracting wrist diminished SICI compared with the no-mirror contraction and the mirror and no-mirror resting conditions. Viewing the mirror at rest did not affect IHI. Conclusions: Seeing the mirror image of the contracting right wrist modulates one specific inhibitory path, SICI, in the right Ml without modifying corticospinal excitability and another inhibitory path, IHI. These findings provide a mechanistic basis for intracortical differences between effortful unilateral shortening contractions with and without a mirror, and may be one of the neural mechanisms responsible for the therapeutic effects of mirror training.

Item Type:	Thesis (Thesis)
Supervisor name:	Supervisor: and Hortobagyi, Prof. Dr. Tibor and Center for Human Movement Sciences, University Medical Cente and University of Groningen, Groningen
Supervisor name:	Co-supervisor: and Dr. Glyn Howatson and Department of Sport, Exercise and Rehabilitation and Sciences, Northumbria University
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 10:57
Last Modified:	25 Jun 2020 10:57
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/1737

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